Floating CSS banners cause landmarks to be obsured when scrolled

[matatk]

One problem with sites that employ a banner that hovers above the page content, and stays fixed when the page scrolls, is that this does not interact well with Landmarks' scrolling the top of a landmark region into view—the top of the region can appear behind the banner.

Have thought of some potential heuristics for this, but it starts to feel a bit ropey and may have unforseen consequences on some sites. Might need some time and experimentation...

[matatk]

Here are some example pages...

• https://www.apple.com/uk/
• https://ng-bootstrap.github.io/#/components/modal/examples